The present embodiments relate to an arrangement of a plurality of split ring resonators on a planar substrate.
Magnetic resonance tomography (MRT) has already been in use in radiology for a length of time. Magnetic resonance tomography is based on very strong magnetic fields and alternating magnetic fields in the radio frequency range that are used to excite specific atomic nuclei (e.g., mostly hydrogen nuclei/protons) in the body to move by resonance. The movement induces an electric signal in a receiver circuit. Specific MRT methods have been developed to be able to display information relating to the microstructure and function of the organs in addition to displaying position and shape.
In order to provide a high quality of the images made with the aid of magnetic resonance tomography, antenna arrays that have a low signal-to-noise ratio are being developed. Increasing the magnetic field strength, however, is automatically accompanied by an increase in the design space for the magnetic resonance tomographs with control, in addition, that is also more complex. A further possibility, specifically the lengthening of the read and/or scan time, may not be justified since the service life and/or efficiency of a magnetic resonance tomograph is greatly restricted. A further approach is to employ small receive antennas, since the small receive antennas have a smaller “field of view.” Reducing the antenna and/or coil field of view also reduces the negative effects (e.g., noise). However, this solution may not be employed in the case of relatively large objects and/or fields of view.
A plurality of antennas or antenna arrays has been employed in order also to be able to scan relatively large fields of view and/or objects. However, increasing the number of antennas gives rise, owing to the inductive coupling and thus influence from the individual antennas, to harmful side effects that restrict an increase in performance regarding the quality of information and/or images.
The attempts to date to decouple the individual antennas have been very complicated and expensive.
Owing to the high achievable level of image quality in magnetic resonance tomography, antenna arrays employed the use of a plurality of split ring resonators (SRRs). Such resonators or resonant circuits include two opposite metal conductor elements that may be applied parallel to one another on opposite sides of a substrate and act as capacitive elements, while the two opposite metal conductor elements simultaneously also act as inductive elements. The conductor elements themselves are formed as separated ring structures. The SRRs are supplied with energy by high frequency (HF) wave radiation, thus being excited to resonant vibrations.
Decoupling the SRRs has been complicated and costly. Thus, in magnetic resonance tomography, conventional loops with DC isolation may be used. A single-layer substrate is sufficient (see U.S. Pat. No. 8,035,382 B2). Because of the double-sided conductor track guidance, a multilayer substrate is used when decoupling the SRRs by geometric overlapping. HF substrates are, however, complicated to produce, and therefore very expensive. In the case of a multilayer substrate (e.g., printed circuit board), the SRRs on the individual layers are to have different dimensions since different resonant frequencies are produced given an identical embodiment in the different layers. Given octagonal loops, a further printed circuit board of, for example, at least four layers is used. In order to reduce the number of layers, the octagonal loops may be reduced by a longitudinal capacitance or smaller capacitive individual loops. Disregarding the production costs, this solution further uses complicated matching.